1. Field of the Invention
The present invention relates to an electronic balance, and more particularly, to an electronic balance capable of performing an automatic high-precision correction of a measured value by reference to one or more loaded reference weights, wherein a positive or negative addition of the reference weight or weights is signalized at a desired interval or alternatively in response to each measurement.
2. Description of the Prior Art
In the known optical or electric balances in which a decline on the scale is visually read, deviations from the reference weight tend to increase its non-linear tendency as a more strict reading is required or as an expected resolution to the full scale is finer. The non-linear tendency is likely to adversely affect the performance of a high resolution balance, such as a microbalance or a semi-microbalance. In a known type of electromagnet balance the non-linear tendency is likewise a problem, which is caused by unavoidable characteristics of its components and circuits.
Under the known balances, therefore, it is required to obtain a corrected curve by reference to the reference weight before an object is weighed on the balance. This is trouble-some and time-consuming.
In addition, the accuracy of the known balances depends upon the accurate measurement of loaded reference weights, and accordingly, it is essential to employ reference weights whose masses are precisely measured. Such reference weights are expensive, thereby increasing the production cost. Even if such expensive reference weights are employed, their masses are subjected to variation due to wearing-out for a long period of use. The readjustment is frequently required.
In general, an electronic balance is subjected to thermal changes in the room temperatures and/or those occurring within the balance itself. Such thermal changes affect the sensitivity of the balance. To overcome the problems likely to occur due to thermal changes, it is required to warm up the balance before use, and to wait for thermal stabilization. When the stabilization is obtained, a manual correction is performed. The lack of this manual correction leads to an inaccurate measurement.
The present invention aims at overcoming the problems and difficulties mentioned above with respect to the known balances, and has for its object to provide an improved electronic balance capable of automatic correction by reference to one or more loaded reference weights in a simplified procedure.
Another object of the present invention is to provide an improved electronic balance which can be operated without the necessity for warming up until a thermal stability is reached, thereby permitting of immediate accurate measurement.
A further object of the present invention is to provide an improved electronic balance of simplified construction without the use of extra components for manual correction, such as variable resistors, thereby simplifying the adjustment of measuring sensitivity.
Other objects and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for the purpose of illustration only, preferred embodiments in accordance with the present invention.